1. Field of the Invention
The present invention generally relates to a positioning system. More specifically, the present invention relates to a positioning system, a positioning apparatus, a positioning information providing apparatus, a positioning method, a control program for the positioning system, and a computer readable recording medium having recorded therein the control program for the positioning system.
2. Background Information
Conventionally, a Global Positioning System (GPS) device has been used as a positioning system that utilizes an artificial satellite to measure a position. In the GPS, an initial position of a positioning apparatus is necessary in order to acquire a GPS satellite and to use the initial position as an initial value for position calculation. A previous positioning position is often used as the initial position. In a car navigation system, in general, positioning is performed repeatedly at short time intervals. Thus, even if a previous position is used as the initial position, a distance between an actual position of the positioning apparatus and the initial position is generally small and no specific problems result. However, for example, in the case of a portable terminal mounted with the GPS device, when a user moves a long distance in a short time by train or other high speed transportation after performing positioning and performs positioning again after arriving at a destination and if the user uses a previous positioning position as an initial position, a gap between the initial position and an actual position may increase causing troubles in positioning.
Japanese Patent Publication JP-A-2002-311122 (especially FIG. 6, etc.) discloses a constitution in which a position of a base station of a cellular phone network is used as an initial position. JP-A-2002-31122 is hereby incorporated by reference.
However, in order to use a position of a base station as an initial position, it is necessary to decide positions of a large number of base stations through location survey and register the respective positions in a database. Thus, there is a problem in that large cost and labor are required.
There is also a problem in that, when a new base station is built or a location of an existing base station is changed, work for location survey and work for updating the database have to be performed every time.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved a positioning system, a positioning apparatus, a positioning information providing apparatus, a positioning method, a control program for the positioning system, and a computer readable recording medium having recorded therein the control program for the positioning system. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.